BAGHDAD - A suicide car-bomb attack on an Iraqi army checkpoint in northern Iraq killed 10 soldiers yesterday, police said.

Elsewhere, U.S. ground and air forces killed four suspected insurgents in a battle north of Baghdad, and two Iraqi women and two children apparently died in the cross fire.

Thirteen civilians were killed and 32 wounded in three other bomb attacks in Iraq, police said.

The attack on the Iraqi army checkpoint, which also wounded 10 Iraqi soldiers and five civilians, was in Khalis, 50 miles north of Baghdad.

The city is in Diyala province, which has seen some of the worst violence recently as mostly Sunni militants are believed to have fled to the area since U.S. and Iraqi troops launched a security crackdown in Baghdad on Feb. 14.

On Wednesday, four Iraqi police officers were killed when a suicide bomber struck a police station in the Diyala city of Balad Ruz, 45 miles northeast of Baghdad.

Two days earlier, a double-suicide bombing struck a paratrooper outpost in the province, killing nine U.S. troops. A group linked to al-Qaeda in Iraq claimed responsibility.

In other violence yesterday, four insurgents were killed as the United States targeted suspected al-Qaeda in Iraq fighters near Taji, a U.S. air base 12 miles north of Baghdad, the U.S. command said.

It said two women and two children were believed to have been killed during the fighting.

"Unfortunately al-Qaeda in Iraq continues to use women and children in their illegal activities," U.S. military spokesman Christopher Garver said.

Also yesterday, two suicide bombers attacked an office of the Kurdistan Democratic Party of Massoud Barzani, leader of the autonomous Kurdish region in Iraq, killing three of its guards and wounding five, police said.

The casualties could have been higher if guards had not opened fire on the two attackers, forcing them to detonate their explosives at least 50 yards from the office, police said. The attack occurred in Zumar, a town 45 miles west of Mosul, the capital of Nineveh province.

It was the second suicide attack this week aimed at the KDP in that area.

In central Baghdad, a roadside bomb missed a passing police patrol yesterday morning but killed four civilians and wounded nine in a commercial district, police said.

A car bomb exploded near Baghdad University, killing six civilians and wounding 18, including some students, police said.

Also in Baghdad, U.S. forces killed three insurgents during a gun battle in the Shiite neighborhood of Sadr City, the military said.